Expression and purification of the D4 region of PLD1 and characterization of its interaction with PED-PEA15

Molecular interactions between a diphenyl scaffold and PED/PEA15: Implications for type II diabetes therapeutics targeting PED/PEA15 - Phospholipase D1 interaction

In a recent study, we have identified BPH03 as a promising scaffold for the development of compounds aimed at modulating the interaction between PED/PEA15 (Phosphoprotein Enriched in Diabetes/Phosphoprotein Enriched in Astrocytes 15) and PLD1 (phospholipase D1), with potential applications in type II diabetes therapy. PED/PEA15 is known to be overexpressed in certain forms of diabetes, where it binds to PLD1, thereby reducing insulin-stimulated glucose transport. The inhibition of this interaction reestablishes basal glucose transport, indicating PED as a potential target of ligands capable to recover glucose tolerance and insulin sensitivity. In this study, we employ computational methods to provide a detailed description of BPH03 interaction with PED, evidencing the presence of a hidden druggable pocket within its PLD1 binding surface. We also elucidate the conformational changes that occur during PED interaction with BPH03. Moreover, we report new NMR data supporting the in-silico findings and indicating that BPH03 disrupts the PED/PLD1 interface displacing PLD1 from its interaction with PED. Our study represents a significant advancement toward the development of potential therapeutics for the treatment of type II diabetes.

Interfering PLD1-PED/PEA15 interaction using self-inhibitory peptides: An in silico study to discover novel therapeutic candidates against type 2 diabetes

Diabetes type 2 (T2D) is a very complex disorder with a large number of cases reported worldwide. There are several reported molecular targets which are being used towards drug design. In spite of extensive research efforts, there is no sure shot treatment available. One of the major reasons for this failure or restricted success in T2D research is the identification of a major/breakthrough therapeutic target responsible for the progression of T2D. It has been well documented that one of the major causes mediating the insulin resistance is the interaction of PLD1 with PED/PEA15. Herein, we have performed in silico experiments to investigate the interaction between PLD1 with PED/PEA15. Furthermore, this study has explored pertinent molecular interactions involving the self-derived peptides. The peptides identified in this study are found to be capable of restricting the interaction of these two proteins. Accordingly, the study suggests that the “self-derived peptides” could be used as promising therapeutic candidate(s) against T2D.

Targetting PED/PEA-15 for diabetes treatment

INTRODUCTION

PED/PEA-15 is an ubiquitously expressed protein, involved in the regulation of proliferation and apoptosis. It is commonly overexpressed in Type 2 Diabetes (T2D) and in different T2D-associated comorbidities, including cancer and certain neurodegenerative disorders. Areas covered: In mice, Ped/Pea-15 overexpression impairs glucose tolerance and, in combination with high fat diets, further promotes insulin resistance and T2D. It also controls β-cell mass, altering caspase-3 activation and the expression of pro- and antiapoptotic genes. These changes are mediated by PED/PEA-15-PLD1 binding. Overexpression of PLD1 D4 domain specifically blocks Ped/Pea-15-PLD1 interaction, reverting the effect of Ped/Pea-15 in vivo. D4α, a D4 N-terminal peptide, is able to displace Ped/Pea-15-PLD1 binding, but features greater stability in vivo compared to the entire D4 peptide. Here, we review early mechanistic studies on PED/PEA-15 relevance in apoptosis before focusing on its role in cancer and T2D. Finally, we describe potential therapeutic opportunities for T2D based on PED/PEA-15 targeting. Expert opinion: T2D is a major problem for public health and economy. Thus, the identification of new molecules with pharmacological activity for T2D represents an urgent need. Further studies with D4α will help to identify smaller pharmacologically active peptides and innovative molecules of potential pharmacological interest for T2D treatment.

Molecular basis of the PED/PEA15 interaction with the C-terminal fragment of phospholipase D1 revealed by NMR spectroscopy

PED/PEA15 is a small protein involved in many protein-protein interactions that modulates the function of a number of key cellular effectors involved in major cell functions, including apoptosis, proliferation and glucose metabolism. In particular, PED/PEA15 interacts with the phospholipase D (PLD) isoforms 1 and 2 increasing protein kinase C-α isoform activity and affects both insulin-stimulated glucose transport and glucose-stimulated insulin secretion. The C-terminal portion (residues 712-1074) of PLD1, named D4, is still able to interact with PED/PEA15. In this study we characterized, by means of NMR spectroscopy, the molecular interaction of PED/PEA15 with D4α, a smaller region of D4, encompassing residues 712-818, shown to have the same affinity for PED/PEA15 and to induce the same effects as D4 in PED/PEA15-overexpressing cells. Chemical shift perturbation (CSP) studies allowed to define D4α binding site of PED/PEA15 and to identify a smaller region likely affected by an allosteric effect. Moreover, ELISA-like experiments showed that three 20-mer overlapping synthetic peptides, covering the 762-801 region of D4α, strongly inhibit PED/PEA15-D4α interaction through their binding to PED/PEA15 with KDs in low micromolar range. Finally, molecular details of the interaction of PED/PEA15 with one of the three peptides have been revealed by CSP and saturation transfer difference (STD) analyses.

NMR backbone dynamics studies of human PED/PEA-15 outline protein functional sites

PED/PEA-15 (phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes) is a ubiquitously expressed protein and a key regulator of cell growth and glucose metabolism. PED/PEA-15 mediates both homotypic and heterotypic interactions and is constituted by an N-terminal canonical death effector domain and a C-terminal tail. In the present study, the backbone dynamics of PED/PEA-15 via (15)N R(1) and R(2) and steady-state [(1)H]-(15)N NOE measurements is reported. The dynamic parameters were analyzed using both Lipari-Szabo model-free formalism and a reduced spectral density mapping approach. The results obtained define a polar and charged surface of the death effector domain characterized by internal motions in the micro- to millisecond timescale, which is crucial for the multiple heterotypic functional protein-protein interactions in which PED/PEA-15 is involved. The present study contributes to a better understanding of the molecular basis of the PED/PEA-15 functional interactions and provides a more detailed surface for the design and development of PED/PEA-15 binders.

Residues 762-801 of PLD1 mediate the interaction with PED/PEA15

The interaction of Phospholipase D1 (PLD1) by its C-terminal domain D4 with PED/PEA15 has been indicated as a target for type 2 diabetes. PED/PEA15 is overexpressed in several tissues of individuals affected by type 2 diabetes and its overexpression in intact cells and in transgenic animal models impairs insulin regulation of glucose transport by a mechanism mediated by the interaction with D4 and the consequent increase of protein kinase C-alpha activity. Expression of D4 or administration of a peptide mimicking the PED/PEA15 region involved in this interaction to cells stably overexpressing PED/PEA15 reduces its interaction with PLD1, thereby lowering PKC-alpha activation and restoring normal glucose transport mediated by PKC-zeta. By using D4 deletion mutants, we have restricted the PLD1 region involved in PED/PEA15 interaction to an N-terminal fragment named D4alpha (residues 712-818). This region binds PED/PEA15 with the same efficacy as D4 (K(D) approximately 0.7 microM) and, when transfected in different PED/PEA15-overexpressing cells, it is able to reduce PKC-alpha activity and to restore the sensitivity of PKC-zeta to insulin stimulation, independently of the PI3K/Akt signalling. We also show that the effective disruption of the PED/PEA15-PLD1 interaction can restore the normal ERK1/2 signalling. Finally, using a set of overlapping peptides that cover the D4alpha region, we have further restricted the shortest PED/PEA15-binding site to a segment encompassing residues 762-801, suggesting that a quite limited binding interface mostly contributes to the interaction and can thus be a selective target for the design of effective antagonists.

Grading the commercial optical biosensor literature-Class of 2008: 'The Mighty Binders'

Optical biosensor technology continues to be the method of choice for label-free, real-time interaction analysis. But when it comes to improving the quality of the biosensor literature, education should be fundamental. Of the 1413 articles published in 2008, less than 30% would pass the requirements for high-school chemistry. To teach by example, we spotlight 10 papers that illustrate how to implement the technology properly. Then we grade every paper published in 2008 on a scale from A to F and outline what features make a biosensor article fabulous, middling or abysmal. To help improve the quality of published data, we focus on a few experimental, analysis and presentation mistakes that are alarmingly common. With the literature as a guide, we want to ensure that no user is left behind.

Frontiers: PED/PEA-15, a multifunctional protein controlling cell survival and glucose metabolism

PED/PEA-15 is a 15-kDa ubiquitously expressed protein implicated in a number of fundamental cellular functions, including apoptosis, proliferation, and glucose metabolism. PED/PEA-15 lacks enzymatic function and serves mainly as a molecular adaptor. PED/PEA-15 is an endogenous substrate for protein kinase C (PKC), calcium/calmodulin-dependent protein kinase II (CAM kinase II), and Akt. In particular, PKC phosphorylates PED/PEA-15 at Ser(104) and CAM kinase II or Akt at Ser(116), modifying its stability. Evidence obtained over the past 10 years has indicated that PED/PEA-15 regulates cell survival by interfering with both intrinsic and extrinsic apoptotic pathways. In addition, it may also control cell proliferation by interfering with ERK1/2-mediated pathways. Indeed, PED/PEA-15 has been identified as an ERK1/2 interactor, which modifies its subcellular localization and targeting to a specific subset of substrates. Increased PED/PEA-15 levels may affect tumorigenesis and cancer progression as well as sensitivity to anticancer agents. Moreover, PED/PEA-15 affects astrocyte motility and increases susceptibility to skin carcinogenesis in vivo. PED/PEA-15 expression is regulated at the transcriptional and the posttranslational levels. Increased PED/PEA-15 expression has been identified in individuals with type 2 diabetes early during the natural history of the disease. Evidence generated over the past 10 years indicated that this defect contributes to altering glucose tolerance by impairing insulin action and insulin secretion and might play a role in the development of diabetes-associated neurological disorders. Strategies are being devised to target key signaling events in PED/PEA-15 action aimed at improving glucose tolerance and at facilitating cancer cell death.

Targeting of PED/PEA-15 molecular interaction with phospholipase D1 enhances insulin sensitivity in skeletal muscle cells

Phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (PED/PEA-15) is overexpressed in several tissues of individuals affected by type 2 diabetes. In intact cells and in transgenic animal models, PED/PEA-15 overexpression impairs insulin regulation of glucose transport, and this is mediated by its interaction with the C-terminal D4 domain of phospholipase D1 (PLD1) and the consequent increase of protein kinase C-alpha activity. Here we show that interfering with the interaction of PED/PEA-15 with PLD1 in L6 skeletal muscle cells overexpressing PED/PEA-15 (L6(PED/PEA-15)) restores insulin sensitivity. Surface plasmon resonance and ELISA-like assays show that PED/PEA-15 binds in vitro the D4 domain with high affinity (K(D) = 0.37 +/- 0.13 mum), and a PED/PEA-15 peptide, spanning residues 1-24, PED-(1-24), is able to compete with the PED/PEA-15-D4 recognition. When loaded into L6(PED/PEA-15) cells and in myocytes derived from PED/PEA-15-overexpressing transgenic mice, PED-(1-24) abrogates the PED/PEA-15-PLD1 interaction and reduces protein kinase C-alpha activity to levels similar to controls. Importantly, the peptide restores insulin-stimulated glucose uptake by approximately 70%. Similar results are obtained by expression of D4 in L6(PED/PEA-15). All these findings suggest that disruption of the PED/PEA-15-PLD1 molecular interaction enhances insulin sensitivity in skeletal muscle cells and indicate that PED/PEA-15 as an important target for type 2 diabetes.